There are many methods developed for detecting the end of the magnetic tape when the tape in the cassette is fully wound onto the take-up reel of the apparatus. One of them has an optical device arranged close to the tape path for detecting the difference of optical character between the portion where magnetic particles are coated and the leader portions which are attached at both ends of the coating portion. For detecting the actual tape end, such devices have to distinguish whether the detected leader portion is attached at the beginning of the coating portion or at the end. Usually, an electronic device is coupled with the optical device for that purpose, which includes, for example, an integration circuit having a certain time constant which provides enough time for the leader portion attached at the beginning of the coating portion to pass through the optical device for preventing misoperation.
Of course, the above mentioned device can be used for an apparatus of automatic reversing type which will automatically change the direction at the tape end, but it is desired for such an apparatus that the change of direction shall occur as soon as possible following the end of the coating portion.
Various electronic circuits, for example, a combination of a differential or integration circuit and a logic circuit, are developed to resolve the problem. However, each of these circuits, added only for detecting the end of the coating portion is complicated and expensive, and would be reflected in an undesirable increase in the price of the apparatus.